Upgrade to OpenSearch 2.0

[lezzago]

Issue #, if available:
#313 - OpenSearch 2.0 Upgrade
#325 - Remove JDK 8 support
Description of changes:

• Build Alerting for OS 2.0
  CheckList:
  [X] Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[lezzago]

Security tests are failing due to the security plugin not built for 2.0 yet.

[codecov-commenter]

Codecov Report

Merging #352 (be980d5) into main (9487c00) will increase coverage by 0.69%.
The diff coverage is 22.22%.

@@             Coverage Diff              @@
##               main     #352      +/-   ##
============================================
+ Coverage     78.27%   78.97%   +0.69%     
- Complexity      265      267       +2     
============================================
  Files           176      176              
  Lines          7223     7286      +63     
  Branches        960     1016      +56     
============================================
+ Hits           5654     5754     +100     
+ Misses         1069     1005      -64     
- Partials        500      527      +27     

Impacted Files	Coverage Δ
...ensearch/alerting/action/AcknowledgeAlertAction.kt	100.00% <ø> (+33.33%)	⬆️
...nsearch/alerting/action/DeleteDestinationAction.kt	100.00% <ø> (+33.33%)	⬆️
.../opensearch/alerting/action/DeleteMonitorAction.kt	100.00% <ø> (+33.33%)	⬆️
...opensearch/alerting/action/ExecuteMonitorAction.kt	100.00% <ø> (+33.33%)	⬆️
.../org/opensearch/alerting/action/GetAlertsAction.kt	100.00% <ø> (+33.33%)	⬆️
...pensearch/alerting/action/GetDestinationsAction.kt	100.00% <ø> (+33.33%)	⬆️
...pensearch/alerting/action/GetEmailAccountAction.kt	100.00% <ø> (+33.33%)	⬆️
.../opensearch/alerting/action/GetEmailGroupAction.kt	100.00% <ø> (+33.33%)	⬆️
...org/opensearch/alerting/action/GetMonitorAction.kt	100.00% <ø> (+33.33%)	⬆️
...ensearch/alerting/action/IndexDestinationAction.kt	100.00% <ø> (+33.33%)	⬆️
... and 134 more

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